ESS200A
Prof. Jin-Yi Yu
Characteristics of
the Gyres
qCurrents are in geostropic balance
qEach gyre includes 4 current components:
two boundary
currents: western and eastern
two transverse
currents: easteward and westward
Western
boundary current (jet stream of ocean)
the fast, deep,
and narrow current moves warm water polarward (transport ~50 Sv or greater)
Eastern
boundary current
the slow, shallow,
and broad current moves cold water equatorward
(transport ~ 10-15 Sv)
Trade
wind-driven current
the moderately
shallow and broad westward current (transport ~ 30
Sv)
Westerly-driven
current
the wider and
slower (than the trade wind-driven current) eastward
current
(Figure
from Oceanography by Tom Garrison)
Volume transport unit:
1 sv = 1 Sverdrup = 1 million m3/sec
(the Amazon river has a
transport of ~0.17 Sv)